Tracheal Mucociliary Transport Research Articles

Variability in tracheal mucociliary transport is not controlled by beating cilia in lambs in vivo during ventilation with humidified and nonhumidified air.

Mucociliary transport in the respiratory epithelium depends on beating of cilia to move a mucus layer containing trapped inhaled particles toward the mouth. Little is known about the relationship between cilia beat frequency (CBF) and mucus transport velocity (MTV) in vivo under normal physiological conditions and when inspired air is dry or not fully humidified. This study was designed to use video-microscopy to simultaneously measure CBF and MTV in the tracheal epithelium through an implanted optical window in mechanically ventilated lambs. The inspired air in 6 animals was heated to body temperature and fully saturated with water for 4 hours as a baseline. In another series of experiments, 5 lambs were ventilated with air at different temperatures and humidities and the mucosal surface temperature was monitored with infrared macro-imaging. In the baseline experiments, during ventilation with fully humidified air at body temperature, CBF remained constant, mean 13.9 ± 1.6 Hz but MTV varied considerably between 0.1 and 26.1 mm/min with mean 11.0 ± 3.9 mm/min, resulting in a maximum mucus displacement of 34.2 µm/cilia beat. Fully humidified air at body temperature prevented fluctuations in the surface temperature during breathing indicating a thermodynamic balance in the airways. When lambs were ventilated with dryer air, the mucosal surface temperature and MTV dropped without a significant change in CBF. When inspired air was dry, mainly latent heat (92%) was transferred to air in the trachea, reducing the surface temperature by 5 °C. Reduced humidity of the inspired air lowered the surface temperature and reduced MTV in the epithelium during ventilation.

Towards automated in vivo tracheal mucociliary transport measurement: Detecting and tracking particle movement in synchrotron phase-contrast x-ray images

Accurate in vivo quantification of airway mucociliary transport (MCT) in animal models is important for understanding diseases such as cystic fibrosis, as well as for developing therapies. A non-invasive method of measuring MCT behaviour, based on tracking the position of micron sized particles using synchrotron x-ray imaging, has previously been described. In previous studies, the location (and path) of each particle was tracked manually, which is a time consuming and subjective process.Here we describe particle tracking methods that were developed to reduce the need for manual particle tracking. The MCT marker particles were detected in the synchrotron x-ray images using cascade classifiers. The particle trajectories along the airway surface were generated by linking the detected locations between frames using a modified particle linking algorithm. The developed methods were compared with the manual tracking method on simulated x-ray images, as well as on in vivo images of rat airways acquired at the SPring-8 Synchrotron.The results for the simulated and in vivo images showed that the semi-automatic algorithm reduced the time required for particle tracking when compared with the manual tracking method, and was able to detect MCT marker particle locations and measure particle speeds more accurately than the manual tracking method. Future work will examine the modification of methods to improve particle detection and particle linking algorithms to allow for more accurate fully-automatic particle tracking.

High-resolution mucociliary transport measurement in live excised large animal trachea using synchrotron X-ray imaging

BackgroundThe Australian Synchrotron Imaging and Medical Beamline (IMBL) was designed as the world’s widest synchrotron X-ray beam, enabling both clinical imaging and therapeutic applications for humans as well as the imaging of large animal models. Our group is developing methods for imaging the airways of newly developed CF animal models that display human-like lung disease, such as the CF pig, and we expect that the IMBL can be utilised to image airways in animals of this size.MethodsThis study utilised samples of excised tracheal tissue to assess the feasibility, logistics and protocols required for airway imaging in large animal models such as pigs and sheep at the IMBL. We designed an image processing algorithm to automatically track and quantify the tracheal mucociliary transport (MCT) behaviour of 103 μm diameter high refractive index (HRI) glass bead marker particles deposited onto the surface of freshly-excised normal sheep and pig tracheae, and assessed the effects of airway rehydrating aerosols.ResultsWe successfully accessed and used scavenged tracheal tissue, identified the minimum bead size that is visible using our chosen imaging setup, verified that MCT could be visualised, and that our automated tracking algorithm could quantify particle motion. The imaging sequences show particles propelled by cilia, against gravity, up the airway surface, within a well-defined range of clearance speeds and with examples of ‘clumping’ behaviour that is consistent with the in vivo capture and mucus-driven transport of particles.ConclusionThis study demonstrated that the wide beam at the IMBL is suitable for imaging MCT in ex vivo tissue samples. We are now transitioning to in vivo imaging of MCT in live pigs, utilising higher X-ray energies and shorter exposures to minimise motion blur.

Mechanisms of airway responses to esophageal acidification in cats.

Acid in the esophagus causes airway constriction, tracheobronchial mucous secretion, and a decrease in tracheal mucociliary transport rate. This study was designed to investigate the neuropharmacological mechanisms controlling these responses. In chloralose-anesthetized cats (n = 72), we investigated the effects of vagotomy or atropine (100 μg·kg(-1)·30 min(-1) iv) on airway responses to esophageal infusion of 0.1 M PBS or 0.1 N HCl at 1 ml/min. We quantified 1) diameter of the bronchi, 2) tracheobronchial mucociliary transport rate, 3) tracheobronchial mucous secretion, and 4) mucous content of the tracheal epithelium and submucosa. We found that vagotomy or atropine blocked the airway constriction response but only atropine blocked the increase in mucous output and decrease in mucociliary transport rate caused by esophageal acidification. The mucous cells of the mucosa produced more Alcian blue- than periodic acid-Schiff (PAS)-stained mucosubstances, and the mucous cells of the submucosa produced more PAS- than Alcian blue-stained mucosubstances. Selective perfusion of the different segments of esophagus with HCl or PBS resulted in significantly greater production of PAS-stained mucus in the submucosa of the trachea adjacent to the HCl-perfused esophagus than in that adjacent to the PBS-perfused esophagus. In conclusion, airway constriction caused by esophageal acidification is mediated by a vagal cholinergic pathway, and the tracheobronchial transport response is mediated by cholinergic receptors. Acid perfusion of the esophagus selectively increases production of neutral mucosubstances of the apocrine glands by a local mechanism. We hypothesize that the airway responses to esophageal acid exposure are part of the innate, rather than acute emergency, airway defense system.

Effect of Clenbuterol on Tracheal Mucociliary Transport in Horses Undergoing Simulated Long‐Distance Transportation

Pneumonia is observed in horses after long-distance transportation in association with confinement of head position leading to reduction in tracheal mucociliary clearance rate (TMCR). Clenbuterol, a beta-2 agonist shown to increase TMCR in the horse, will ameliorate the effects of a fixed elevated head position on large airway contamination and inflammation in a model of long-distance transportation model. Six adult horses. A cross-over designed prospective study. Horses were maintained with a fixed elevated head position for 48 hours to simulate long-distance transport, and treated with clenbuterol (0.8 μg/kg PO q12h) or a placebo starting 12 hours before simulated transportation. TMCR was measured using a charcoal clearance technique. Data were collected at baseline and 48 hours, and included TMCR, tracheal wash cytology and quantitative culture, rectal temperature, CBC, fibrinogen, and serum TNFα, IL-10, and IL-2 levels. There was a 18-21 day washout between study arms, and data were analyzed using regression analysis and Wilcoxon rank-sum tests. Tracheal mucociliary clearance rate was significantly decreased after transportation in both treatment (P = .002) and placebo (P = .03) groups. There was a significant effect of treatment on TMCR, with the treatment group showing half the reduction in TMCR compared with the placebo group (P = .002). Other significant differences between before- and after-transportation samples occurred for serum fibrinogen, peripheral eosinophil count, quantitative culture, tracheal bacteria, and degenerate neutrophils, though no treatment effect was found. Treatment with clenbuterol modestly attenuates the deleterious effects of this long-distance transportation model on tracheal mucociliary clearance.

Effects of different mechanical ventilation strategies on the mucociliary system

To evaluate the effects of different mechanical ventilation (MV) strategies on the mucociliary system. Experimental study. Twenty-seven male New Zealand rabbits. After anesthesia, animals were tracheotomized and ventilated with standard ventilation [tidal volume (Vt) 8 ml/kg, positive end expiratory pressure (PEEP) 5 cmH(2)O, flow 3 L/min, FiO(2) 0.4] for 30 min. Next, animals were randomized into three groups and ventilated for 3 h with low volume (LV): Vt 8 ml/kg, PEEP 5 cmH(2)O, flow 3 L/min (n = 6); high volume (HV): Vt 16 ml/kg, PEEP 5 cmH(2)O, flow 5 L/min (n = 7); or high pressure (HP): Ppeak 30 cmH(2)O, PEEP 12 cmH(2)O (n = 8). Six animals (controls) were ventilated for 10 min with standard ventilation. Vital signals, blood lactate, and respiratory system mechanics were verified. Tracheal tissue was collected before and after MV. Lung and tracheal tissue sections were stained to analyze inflammation and mucosubstances by the point-counting method. Electron microscopy verified tracheal cell ultrastructure. In situ tracheal ciliary beating frequency (CBF), determined using a videoscopic technique, and tracheal mucociliary transport (TMCT), assessed by stereoscopic microscope, were evaluated before and after MV. Respiratory compliance decreased in the HP group. The HV and HP groups showed higher lactate levels after MV. Macroscopy showed areas of atelectasis and congestion on HV and HP lungs. Lung inflammatory infiltrate increased in all ventilated groups. Compared to the control, ventilated animals also showed a reduction of total and acid mucus on tracheal epithelium. Under electron microscopy, injury was observed in the ciliated cells of the HP group. CBF decreased significantly after MV only in the HP group. TMCT did not change significantly in the ventilated groups. Different MV strategies induce not only distal lung alterations but also morphological and physiological tracheal alterations leading to mucociliary system dysfunction.

Vicks VapoRub Induces Mucin Secretion, Decreases Ciliary Beat Frequency, and Increases Tracheal Mucus Transport in the Ferret Trachea

Vicks VapoRub (VVR) [Proctor and Gamble; Cincinnati, OH] is often used to relieve symptoms of chest congestion. We cared for a toddler in whom severe respiratory distress developed after VVR was applied directly under her nose. We hypothesized that VVR induced inflammation and adversely affected mucociliary function, and tested this hypothesis in an animal model of airway inflammation. [1] Trachea specimens excised from 15 healthy ferrets were incubated in culture plates lined with 200 mg of VVR, and the mucin secretion was compared to those from controls without VVR. Tracheal mucociliary transport velocity (MCTV) was measured by timing the movement of 4 microL of mucus across the trachea. Ciliary beat frequency (CBF) was measured using video microscopy. [2] Anesthetized and intubated ferrets inhaled a placebo or VVR that was placed at the proximal end of the endotracheal tube. We evaluated both healthy ferrets and animals in which we first induced tracheal inflammation with bacterial endotoxin (a lipopolysaccharide [LPS]). Mucin secretion was measured using an enzyme-linked lectin assay, and lung water was measured by wet/dry weight ratios. [1] Mucin secretion was increased by 63% over the controls in the VVR in vitro group (p < 0.01). CBF was decreased by 35% (p < 0.05) in the VVR group. [2] Neither LPS nor VVR increased lung water, but LPS decreased MCTV in both normal airways (31%) and VVR-exposed airways (30%; p = 0.03), and VVR increased MCTV by 34% in LPS-inflamed airways (p = 0.002). VVR stimulates mucin secretion and MCTV in the LPS-inflamed ferret airway. This set of findings is similar to the acute inflammatory stimulation observed with exposure to irritants, and may lead to mucus obstruction of small airways and increased nasal resistance.

Airway responses to esophageal acidification

The effects of esophageal acidification on airway function are unclear. Some have found that the esophageal acidification causes a small increase in airway resistance, but this change is too small to cause significant symptoms. The aims of this study were to investigate the effects of esophageal acidification on multiple measures of airway function in chloralose-anesthetized cats. The esophagus was cannulated and perfused with either 0.1 M PBS or 0.1 N HCl at 1 ml/min as the following parameters were quantified in separate experiments: diameter of bronchi (n = 5), tracheal mucociliary transport rate (n = 4), tracheobronchial mucus secretion (n = 7), and lung function (n = 6). We found that esophageal acidification for 10-30 min decreased bronchial diameters primarily of the smaller low-resistance airways (10-22%, P < 0.05), decreased tracheal mucociliary transport (53%, 8.7 +/- 2.4 vs. 4.1 +/- 1.3 mm/min, P < 0.05), increased tracheobronchial mucus secretion (147%, 3.4 +/- 0.7 vs. 8.4 +/- 2.6 mg/10 min, P < 0.05), and caused no change in total lung resistance or dynamic compliance (P > 0.05). Considering that tracheal mucociliary transport rate is governed in part by mucus secretion, we concluded that the primary airway response to esophageal acidification observed is increased mucus secretion. Airway constriction may act to assist in rapid secretion of mucus and to increase the effectiveness of coughing while not affecting lung resistance or compliance. Given the buffering capabilities of mucus, esophageal acidification activates appropriate physiological responses that may act to neutralize gastroesophageal reflux that reaches the larynx, pharynx, or lower airways.

Effect of needle puncture and electro-acupuncture on mucociliary clearance in anesthetized quails.

BackgroundAcupuncture therapy for obstructive respiratory diseases has been effectively used in clinical practice and the acupuncture points or acupoints of Zhongfu and Tiantu are commonly-used acupoints to treat patients with the diseases. Since the impaired mucociliary clearance is among the most important features of airway inflammation in most obstructive respiratory diseases, the effect of needle puncture and electro-acupuncture at the specific acupoints on tracheal mucociliary clearance was investigated in anesthetized quails.MethodsMucociliary transport velocity on tracheal mucosa was measured through observing the optimal pathway, and fucose and protein contents in tracheal lavages were determined with biochemical methods. In the therapeutic group, needle puncture or electro-acupuncture stimulation to the acupoints was applied without or with constant current output in 2 mA and at frequency of 100 Hz for 60 minutes. In the sham group, electro-acupuncture stimulation to Liangmen was applied.ResultsOur present experiments demonstrated that the electro-acupuncture stimulation to Zhongfu and Tiantu significantly increased tracheal mucociliary transport velocity and decreased the content of protein in the tracheal lavage, compared with the control group. Moreover, either needle puncture or electro-acupuncture stimulation to Zhongfu and Tiantu significantly reverted the human neutrophil elastase-induced decrease in tracheal mucociliary transport velocity and human neutrophil elastase -induced increase in the contents of fucose and protein in the tracheal lavage, compared with the control group.ConclusionThese results suggest that either needle puncture or electro-acupuncture stimulation to the effective acupoints significantly improves both airway mucociliary clearance and the airway surface liquid and that the improvements maybe ascribed to both the special function of the points and the substantial stimulation of electricity.

Evaluation of a Mucoactive Herbal Drug, Radix Ophiopogonis, in a Pathogenic Quail Model

We investigated the effect of Radix Ophiopogonis on airway mucociliary clearance and mucus secretion in anesthetized quails. The oral administration of 10 g/kg of Radix Ophiopogonis significantly increased tracheal mucociliary transport velocity (MTV). Moreover, either 10 g/kg or 3 g/kg of Radix Ophiopogonis markedly attenuated the human neutrophil elastase (HNE)-induced decrease in MTV. Furthermore, we found that 10 g/kg of Radix Ophiopogonis significantly abolished the HNE-induced increases in fucose and protein contents of tracheal lavage, whereas Radix Ophiopogonis at the same dose only significantly decreased the protein content in the control group. These results suggest that Radix Ophiopogonis improves airway mucociliary clearance and that the improvement may, at least in part, be ascribed to the amelioration of airway mucus secretion.

Mucociliary Transport Pathway on Laryngotracheal Tract and Stented Glottis in Guinea Pigs

We investigated the laryngotracheal mucociliary transport pathway of guinea pigs in vivo and immediately postmortem. Only intraperitoneal anesthesia was used during the procedure to avoid the disturbance of mucociliary function. Resin particles were used as the marking substance. A microcolpohysteroscope was placed at different levels in the laryngotracheal region for observing the marking particles and recording the transport pattern. The tracheal mucociliary transport flow primarily moved along the posterior wall and both lateral walls in a zigzag trace. Upon reaching the subglottis, the resin particles stayed underneath the vocal cords, and a whirlpool phenomenon developed. The majority of the particles were shifted and directed onto the posterior glottic area. With a short delay, some resin particles crossed over the free edge of the vocal cords and turned posteriorly along the medial upper cordal margin. No mucociliary transport could be observed on the entire upper surface of the true vocal cords, which is covered by squamous epithelium. Occasionally, a few resin particles in the vicinity of the epiglottic root traveled along the aryepiglottic folds toward the posterior commissure. All streams of mucociliary transport finally joined together in the interarytenoid area. After leaving the glottis, the resin particles traveled to the hypopharynx and entered the esophagus through the motion of deglutition. The pattern of mucociliary clearance in the laryngotracheal region was not delayed by stenting.

YM-40461, a potent surfactant secretagogue, improves mucociliary clearance in SO2-exposed guinea pigs.

The effects of the new pulmonary surfactant secretagogue YM-40461, 1-(2-dimethylaminoethyl)-1-(3,4,5-trimethoxyphenyl) urea, on tracheal mucociliary transport (MCT) were assessed using guinea pigs with acute bronchitis. Acute bronchitis was induced by SO2 gas exposure (400 ppm for 3 h). MCT velocity was measured by means of the dye gelatin technique. YM-40461 at doses of 1-10 mg/kg, p.o. induced recovery of MCT function, with an ED50 value of 2.4 mg/kg. Maximal recovery (78.0+/-12.5%) was observed 2 h in the animals treated with 10 mg/kg of YM-40461. Ambroxol and bromhexine showed less effect on the MCT dysfunction than YM-40461. An artificial surfactant (Surfacten) also aided recovery. YM-40461 at a dose of 10 mg/kg, p.o. significantly improved surfactant production without affecting mucus secretion. These results show that YM-40461 ameliorates MCT dysfunction caused by SO2 exposure by activation of pulmonary surfactant secretion.

The effect of maimendongtang on airway clearance and secretion.

We investigated the effect of Maimendongtang on airway clearance and secretion in anaesthetized quails. The oral application of 1 g/kg of Maimendongtang significantly increased tracheal mucociliary transport velocity (MCTV), whereas 100 or 300 mg/kg of Maimendongtang failed to do so. Moreover, 300 mg/kg or 1 g/kg of Maimendongtang markedly attenuated human neutrophil elastase (HNE) or DNA-induced decrease in MCTV although 100 mg/kg of Maimendongtang had little effect. Furthermore, we found that Maimendongtang significantly restored HNE-induced increases in DNA, fucose and protein contents of airway surface fluid (ASF), whereas only Maimendongtang itself significantly decreased the protein content. These results indicate that Maimendongtang increases MCTV and the increase may be, at least in part, ascribed to the amelioration of ASF in the trachea.

O-182 - Effects of lysozyme chloride on foreign materials excretion by tracheal mucociliary transport

O-182 - Effects of lysozyme chloride on foreign materials excretion by tracheal mucociliary transport

Effect of Human Neutrophil Elastase on Tracheal Mucociliary Transport in Anesthetized Quails

We investigated the effect of human neutrophil elastase (HNE) on tracheal mucociliary transport in anesthetized quails. Topical application of HNE (30-300/μg/kg) to tracheal mucosa dose-dependently decreased mucociliary transport velocity (MCTV). The HNE (300 μg/kg)-induced decrease in MCTV was blocked by ONO-5046 · Na (sodium N-[2-[4-(2,2-dimethylpropionyloxy)phenyl-sulfonylamino]-benzoyl]aminoacetate tetrahydrate) (3-30mg/kg, i.m.), a specific neutrophil elastase inhibitor. Furthermore, we found that HNE increased DNA, fucose and protein contents of tracheal lavages, and the increases were also reverted by ONO-5046·Na. These results indicated that HNE decreased tracheal mucociliary transport, and the decrease may be, at least in part, ascribed to the deterioration of tracheal secretions.

Effects of posture and accumulated airway secretions on tracheal mucociliary transport in the horse.

Tracheal mucociliary clearance was determined in horses by measuring the rostrad transport of the radiopharmaceutical 99mtechnetium-sulphur colloid following deposition on the tracheal epithelium by intratracheal injection. The effects of head position (head elevated to normal standing position vs head lowered) and of accumulated purulent secretions on tracheal mucociliary clearance were evaluated for the first time in the horse. In normal horses tracheal mucociliary clearance was greatly accelerated by lowering the head so that the cranial trachea was lower than the caudal trachea. Horses confined with their heads elevated for 24 hours developed an accumulation of purulent airway secretions (and associated increased numbers of bacteria) in the lower respiratory tract and showed a decrease in tracheal mucociliary clearance when compared with their previously measured rate when the lower airway contained only normal secretions. These findings have implications for management practices where horses are prevented from lowering their heads, such as transportation and cross-tying, which may therefore contribute to lower respiratory tract disease in horses.

Effect of Leukotriene D4 on Tracheal Mucociliary Transport Velocity in Quails

We investigated the effect of leukotriene D4 (LTD4) on tracheal mucociliary transport in quails. Topical application of LTD4 (0.2-2 ng) to tracheal mucosa dose-dependently increased mucociliary transport velocity (MCTV) in 5 or 10 min after application. Forty minutes after application of 2 ng of LTD4, MCTV was decreased to about 84% of that in the control group. Both the transient increase and the subsequent decrease induced by 2 ng of LTD4 were blocked by ONO-1078 (Pranlukast: 4-oxo-8-[4-(4-phenylbutoxy)-benzoylamino]-2-(tetrazol-5-yl)- 4H- 1-benzopyran) (0.03-3 mg/kg, i.m.), a specific leukotriene antagonist. These results suggest that LTD4 possesses a biphasic effect on tracheal mucociliary transport through leukotriene receptors.

Inspired anaesthetic gas humidification improves thermal uniformity during canine whole body hyperthermia.

Supplying warmed saturated water vapour in anaesthetic gases during whole body hyperthermia (WBH) could potentially improve thermal uniformity in the trachea and esophagus. Four normal dogs were anaesthetized for WBH at 42 degrees C. A Puritan Bennett Cascade humidifier was used to supply anaesthetic gases saturated with water vapour at an average airway temperature of either 42 degrees C or 38 degrees C. Esophageal temperature was monitored at the thoracic inlet and 5 cm cephalad. Thermal dose was estimated by calculating equivalent minutes for an isoeffect at 43 degrees C (CEM 43 degrees Tx, where Tx is the site of temperature measurement). Endotracheal mucociliary transport velocity (MCTV) was determined before and 48 h following WBH by 99mTc-MAA scintigraphy. Compared to the 38 degrees C humidified gas group, dogs receiving 42 degrees C humidified gas reached 42 degrees C faster (p = 0.02) and had CEM 43 degrees T(esophageal) values equivalent to the target CEM 43 degrees T(rectal). Endotracheal MCTV with 42 degrees C humidified gas, however, was reduced 53% from baseline 48 h following WBH (p = 0.02). With 38 degrees C humidified gas, endotracheal mucociliary transport velocity was unchanged from baseline 48 h post WBH. Tracheal histology was examined using light and electron microscopy in four additional dogs euthanatized following 90 min of 42 degrees C humidified gas combined with WBH. There was no histological evidence of tracheal or lung thermal damage with 42 degrees C humidified gas in these four dogs. However, a moderate increase in tracheal goblet cell secretory granule staining was observed. This change could imply temporary heat-induced ciliary microtubule dysfunction, rather than decreased mucus production, as the likely mechanism of reduced mucociliary transport velocity 48 h following WBH. Administration of 42 degrees C humidified anaesthetic gases with WBH improves heating rate and esophageal thermal uniformity but temporarily depresses tracheal mucociliary transport velocity.

Tracheal mucociliary transport rate in awake dogs

Summary To measure tracheal mucociliary transport rate (tmtr) in awake dogs, restrained in dorsal recumbency 99mtechnetium-labeled macroaggregated albumin was administered by tracheal injection, and the cephalic movement of boluses containing the radiopharmaceutical was detected by a gamma camera positioned lateral to the dog's head and neck. The distance traveled by each bolus was measured, relative to external markers placed a known distance apart. Tracheal mucociliary transport rates were calculated by dividing the measured distance of radiopharmaceutical movement by elapsed time. The technique was efficient and well tolerated. Mean (± sd) tmtr was 35.3 ± 15.9 mm/min. Significant (P = 0.029) difference in tmtr was found between males and females, but significant difference attributable to age of the dog was not detected. This method of measuring tmtr in awake dogs has potential for evaluation of clinical animal patients with suspected tracheal mucociliary abnormalities.

Influence of corticosterone on tracheal mucociliary transport in pigeons.

The effects of corticosteroids on tracheal mucociliary transport (MCT) were examined in pigeons. Intramuscular administration of corticosterone had no effect at 1.0 mg/kg, while at a larger dose of 5.0 mg/kg, it slightly, but significantly increased the MCT rate. Metyrapone significantly decreased the MCT rate, and the inhibitory action was blocked by 1.0 mg/kg corticosterone. The present study suggested that corticosteroids modulated the mucociliary clearance, especially under some diseases associated with a decreased level of endogenous corticosteroids.